I've been experimenting with running mint inside a chroot in parallel to my debian testing system, and I have just figured out how to do it. This is different from using a virtual machine like virtualbox or Xen - the kernel is the same as the host system but everything else comes from the distro you are chrooting (in this case mint). The advantage is it should run a bit quicker than with virtualbox, and you can switch between the two using ctrl-alt-f8/f7.

First you need to create a free partition on your disk and install mint to it as normal. This is the one step that could be dangerous for your host system, so back everything up first. Ask in this thread if you need help with this step.

Next you need to open a root terminal and mount all the necessary drives and directories (replace /dev/sdxx with the proper kernel name of the partition you have mint on.)

This creates a protected environment inside the chroot, where all the programs think that /mnt is the root directory. Most of mint should run fine inside this chroot, but if you get any problems it's best to check whether it's the fault of the chroot by rebooting and choosing it at boot time.